Composition and method for electrodeposition of zinc

ABSTRACT

An aqueous bath for electroplating zinc includes a soluble zinc salt, a soluble electrolyte and a surface active agent formulation. The zinc salt and electrolyte provide ammonium and chloride ions and the surface active agent formulation is based upon a nonionic block copolymer of ethylene oxide and propylene oxide. In some instances, the block copolymer may be utilized alone, in other instances, it is used in combination with an N(alkyl sulfonyl) glycine compound. Other surface active agents and brighteners are advantageously employed in connection therewith, and the bath may be operated at a pH of 3.0-6.3.

Waited States Patent 91 Hsu et a1.

[ 1 Apr.24,1973

[75] Inventors: Grace F. l-llsu, Somers; Merton M.

Beckwith, Rockville, both of Conn.

[73] Assignee: Conversion Chemical Corporation,

Rockville, Conn.

[22] Filed: Ap. 17, 1972 [21] Appl. No.: 244,870

[52] US. Cl. ..204/55 R [51] Int. Cl. ..C23b 5/12, C23b 5/46 [58] Field of Search ..204/55 R, 43 Z, 44,

[56] References Cited UNITED STATES PATENTS 3.669,854 6/1972 Harbulak ..204/55 R FOREIGN PATENTS OR APPLICATIONS 1,524,718 5/1968 France ..204/55 R 3/1968 Germany ..204/55 R 4/1969 Great Britain ..204/55 R OTHER PUBLICATIONS Chemical Abstracts, 70965V, p. 518, vol. 74 (1971 Primary Examiner-G. L. Kaplan Attorney-Peter L. Costas ABSTRACT An aqueous bath for electroplating zinc includes a soluble zinc salt, a soluble electrolyte and a surface active agent formulation. The zinc salt and electrolyte provide ammonium and chloride ions and the surface active agent formulation is based upon a nonionic block copolymer of ethylene oxide and propylene oxide. In some instances, the block copolymer may be utilized alone, in other instances, it is used in combination with an N-(alkyl sulfonyl) glycine compound. Other surface active agents and brighteners are advantageously employed in connection therewith, and the bath may be operated at a pH of 3.0-6.3.

31 Claims, No Drawings COMPOSITION AND METHOD FOR ELECTRODEPOSITION OF ZINC BACKGROUND OF THE INVENTION Over the years, many baths have been utilized for electroplating zinc onto metallic substrates, and zinc electroplated deposits are widely employed for many industrial applications. At present, the most widely employed bath is one using a cyanide electrolyte despite However, they in turn exhibit low throwing power, a

poor current efficiency at low current densities and a tendency toward secondary anode corrosion as the metal content of the bath increases. Another problem with sulfate baths is their tendency to produce dull zinc deposits.

Inthe copending application of John Gove Poor et al. filed on Dec. 18, 1968 bearing Ser. No. 784,917 and' entitled METHOD AND COMPOSITION FOR ELEC- TROPLATING ZINC, there is disclosed a zinc electroplating bath employing chloride electrolyte and utilizing a novel combination of surface active agents to achieve advantageous zinc electrodepositions over a relatively broad pH. The baths of this application have enjoyed substantial commercial acceptance because of their ability to plate upon cast and malleable iron alloys, to operate at low voltages with satisfactory throwing power and high current efficiency and to operate over a wide range of current density. The depositions produced by these baths have exhibited a satisfactory degree of ductility, adhesion and brightness. Such baths have proven extremely advantageous from the standpoint of minimizing pollution problems.

However, it has been found that the aforementioned baths of the John Gove Poor et al. application do not operate as effectively as might be desired in the weak acid range of a pH of 4.0-6.5 where many manufacturers would prefer to conduct their operations. In addition, there has been a continuing demand for evenwhich produces deposits of specular brightness and which exhibits highly satisfactory leveling action.

Still another object is to provide such a bath which is relatively economical and highly effective for depositing zinc upon cast and malleable iron alloys and which exhibits excellent throwing power.

A further object is to provide a method for electroplating zinc utilizing such improved zinc plating baths to obtain workpieces with highly adherent and ductile zinc deposits at relatively low cost.

SUMMARY OF THE INVENTION It has been found that the foregoing and related objects may be readily attained in an aqueous bath for producing a ductile, adherent zinc electroplated deposit which comprises, on a per liter basis, a soluble zinc salt providing 4-75 grams of zinc as metal and selected from the group consisting of zinc chloride, zinc sulfate, zinc fluoborate, zinc acetate and mixtures thereof. The electrolyte is a soluble ammonium salt of hydrochloric acid, sulfuric acid, fluoboric acid, acetic acid, and mixtures thereof and provides 4-90 grams of ammonium ion. The zinc and ammonium salts provide the designated acid anions in a molar amount at least equal to the combined molar amount of zinc as metal and ammonium ion and within the range of 15-200 grams and provide at least about 15 grams of an anion selected from the group consisting of chloride, fluoborate and mixtures thereof. There is included 2-45 grams of a surface active agent formulation comprising surface active agents selected from the group consisting of (i) nonionic block copolymers of ethylene oxide and propylene oxide having a total molecular weight of about l,500-3,500 and an ethylene oxide content of about 35-45 weight percent thereof; (ii) mixtures of anionic N-(alkyl sulfonyl) glycine compounds with nonionic block copolymers of ethylene oxide and propylene oxide having a total molecular weight of about l,200-l3,000, and ethylene oxide molecular weight of about 500-l0,000, and an ethylene oxide content of about 30-85 weight percent thereof, the total molecular weight being less than about 5,500 when the ethylene oxide content is 30-40 percent by weight thereof; and mixtures of either of surface active agents (i) and (ii) with other surface active agents. The pH of the bath is adjusted to be within the range of 3.0-6.3.

Generally, the preferred baths will be provided by zinc salts which consist at least predominately of zinc chloride and ammonium salts which consist at least predominately of ammonium chloride. However, zinc fluoborate and ammonium fluoborate have also proven highly advantageous in some applications. The amount of zinc salt preferably will provide about -50 grams per liter of zinc as metal and the ammonium salt will preferably provide about 7.5-50 grams per liter of ammonium ion with the acid anion content being about 0.75-l.5 of the combined molar amounts of the zinc and ammonium ions. The pH of the bath is most desirably maintained at about 5.5-5.9.

The bath most effectively includes 002-1 .5 grams of a brightener and the brighteners which have been found most operable are selected from the group consisting of aryl ketones, aryl aldehydes, tetrahydroand ring halogenated aryl ketones and aldehydes, heterocyclic aldehydes and ketones, carbocylic aldehydes and ketones, the aliphatic aldehydes having 4-7 carbon atoms.

The preferred compositions use either the surface active agent (i) which is a block copolymer of relative narrow molecular weight and ethylene oxide content or the combination of the block copolymer of broader molecular weight and ethylene content with the glycine derivative, both in admixture with other surface active agents to further enhance the operation of the bath. These surface active agents comprise amphoteric imidazoline derivatives as defined more fully hereinafter and anionic condensates of naphthalene/sulfonic acid either as the acid or as the soluble salts thereof. Generally, the block copolymer is utilized in an amount of about 2.0-20.0 grams per liter, the glycine compound is utilized in the range of about 0.l-l0.0 grams per liter, the amphoteric imidazoline derivative is utilized in the range of about 0.1-5.0 grams per liter and the naphthalene/sulfonic acid condensate is utilized in an amount of about 0.l'-l0.0 grams per liter.

In the method of the present invention, the aqueous bath is prepared as defined hereinbefore and is maintained at a temperature of about 65l35 Fahrenheit and preferably about 70-90 Fahrenheit. A workpiece having a metallic surface and a zinc anode are immersed in the bath and a potential is applied across the anode and workpiece to provide a cathode current density of about l.0-100.0 amperes per square foot.

Preferably, the cathode current density is about l-SO amperes per square foot, and mild agitation is generally advantageous.

DESCRIPTION OF THE PREFERRED EMBODIMENTS THE ZINC SALTS Generally the bath may be formulated from various zinc salts or from zinc oxide, the latter forming a zinc salt in combination with the anions otherwise introduced. The zinc salts present in the bath are selected from the group consisting of zinc chloride, zinc sulfate, zinc fluoborate, zinc acetate and mixtures thereof. The amount of zinc salts will provide from 4-75 grams per liter of zinc as metal and preferably 7.5-50.0 grams per liter. The baths containing low metal content are particularly useful for barrel plating operations where drag out losses represent a substantial economic problem. However, for most plating operations and particularly for rack plating operations, the zinc metal will comprise about 25-45 grams per liter.

THE ELECTROLYTE In order to provide satisfactory conductivity (and possibly solubility), the baths include an electrolyte which comprises a soluble ammonium salt of any one of hydrochloric acid, sulfuric acid, fluoboric acid, acetic acid, or mixtures thereof. The ammonium salt will generally provide 4-90 grams per liter of ammonium ion and preferably about 25-75 grams per liter.

It will be appreciated that the ammonium salt will generally comprise the salt of an acid providing the same anion as that of the soluble zinc salt, although different compounds may be utilized in making up the bath. Moreover, the zinc and ammonium salts may be generated in situ by the incorporation of appropriate acids to provide the desired anions.

The electrolyte may utilize as its primary component any one of the named acid salts. However, it has been found necessary to include either ammonium chloride or ammonium fluoborate in order to obtain commercially usable formulations. Generally, the zinc and ammonium salts should provide at least about 15 grams per liter of chloride, fluoborate, or mixtures of chloride and fluoborate ions. Moreover, the salts should also include the acid anions in a molar amount at least equal to the combined molar amount of zinc as metal and ammonium ion and within the range of 15-200 grams per liter. Preferably, the anion of the two salts is present in an amount of about 50-150 grams per liter.

The preferred baths are those in which the zinc and ammonium salts are at least predominantly comprised of the chloride salts. Generally, the total chloride ion content will be about 0.75-l.5 times the combined molar amounts of the zinc and ammonium ions.

THE SURFACE ACTIVE AGENT FORMULATION As previously indicated, the surface active agent formulation may be provided by certain ethylene oxide/propylene oxide block copolymers alone, or by the combination of the block polymers with an N- (alkyl sulfonyl) glycine compound or by a combination of either of these two surface active systems with other surface active agents selected from the group consisting of condensates of naphthalene and sulfonic acid, imidazoline derivatives, and mixtures thereof. Generally, the total surface active agent component will comprise 2-45 grams per liter and preferably about 2.5l0.0 grams per liter.

1. The Ethylene Oxide/Propylene Oxide Block Copolymer The ethylene oxide/propylene oxide block copolymers employed in the present invention are generally described in Lundsted U.S. Pat. No. 2,674,619 granted Apr. 6, 1954. Essentially, these compounds comprise a block polymer of ethylene oxide and a block polymer of propylene oxide and the blocks of ethylene oxide generally appear at either end of the propylene oxide block. Full details concerning the method of preparation and chemical structure can be derived from a study of the aforementioned Lundsted patent. Commercial formulations of the block copolymers are sold by BASF Wyandotte Corporation of Wyandotte, Michigan under the trademark PLURONIC.

When the block copolymer has a molecular weight of about 1,500-3,50O and a structure in which the ethylene oxide content comprises 35-45 weight percent thereof, it has been found that the block copolymer itself will provide adequate surface active properties over a reasonably advantageous plating range. However, the useful properties of even this narrowly defined block copolymer can be extended by admixing with the other surface active agents as more fully described herein.

Other block copolymers of ethylene oxide and propylene oxide have proven useful in the manufacture of the plating baths of the present invention but they generally require the presence of the N-( alkyl sulfonyl) glycine compound as hereinbefore indicated. Thus, a second category of suitably surface active agent formulation utilizes the nonionic block copolymers of ethylene oxide and propylene oxide having a total molecular weight of about l,200-l3,000, an ethylene oxide content of about 30-85 weight percent thereof and an ethylene oxide molecular weight of about SOD-10,000. When the ethylene oxide content is only 30-40 percent by weight of the block copolymer, then the molecular weight must be less than about 5,500 to achieve satisfactory results.

The block copolymers are generally employed in the range of 2-20 grams per liter and preferably about 4-12 grams per liter. The most desirably formulations employ about 7-10 grams per liter, and it has been found that the concentration of this component is essentially independent of metal ion concentration.

2. The Anionic Glycine Compound The anionic glycine compound is the sodium or ammonium salt thereof. Generally, the alkyl chain has 8-l6 carbon atoms and the commercially available materials are frequently mixtures wherein the aliphatic groups average 12 carbon atoms. These compounds are employed in an amount of 0. 1-100 grams per liter and preferably about 0.3-3.0 grams per liter because their solubility tends to be somewhat low. The optimum compositions use about 0.5-1 .0 gram per liter.

When higher concentrations of the glycine compound are employed, it is imperative that at least an equivalent amount of the block copolymer be incorporated in the formulation in order to maintain adequate solubility.

This particular component is found to be extremely effective in broadening the useful plating range at the low current density area. Thus it proves useful not only with the more broadly defined ethylene oxide/propylene oxide block copolymers but also with the relatively narrowly defined block copolymers which are useful in and of themselves. The preferred glycine compounds are the ammonium or sodium salts.

3. The Naphthalene/sulfonic Acid Compounds These compounds are the condensates of naphthalene and sulfonic acid either as the acid or as the alkali metal or ammonium salts. These compounds are usually condensed by the presence of formaldehyde and their molecular weight may vary considerably. The most useful compounds in accordance with the present invention are those having a molecular weight of about 400-l,200 and preferably about 600-900. From the standpoint of avoiding the introduction of unnecessary cations, the ammonium salts have been found preferawith either the ethylene oxide/propylene oxide block copolymers which are useful in and of themselves or with the combination of the block copolymers with the glycine compound. 4. The Imidazoline Derivatives The imidazoline derivatives correspond to the formula:

inc-0H, ornz NIT-CHZCHZY N=C a In the foregoing formula, R represents an alkyl radical having five to 24 carbon atoms; G is the OH ion, an acid salt radical, an anionic surface-active sulfate salt radical such as preferably OSOz-OR, or an anionic surface active sulfonate salt radical; and Z is COOM, Cl-I COOM, or CHOHCH SO M radical. The substituent designated M in the foregoing formula is a hydrogen atom, an alkali metal or an organic base, and that designated Y is. either an -OR' or N(R') A group. Each R substituent is independently selected from the group consisting of hydrogen, alkali metals, and (CH ),,COOM; A represents an anionic monovalent radical and n represents an integer from I to 4. Use of the dotted line representation for the bonds connecting the substituents G and CH Z to the nitrogen atom indicates that these substituents are optionally present or absent, but it should be understood that they are either both present or both absent. Desirable compounds are provided when, in accordance with the foregoing formula, G represents the radical OSO OR, particularly in which R is a C to C alkyl group, and Z is a COOM radical in which M is preferably an alkali metal cation. Exemplary of the compounds corresponding to the foregoing formula which are satisfactory for use in the baths described herein are 2-alkyl-l- (ethyl-beta-oxypropanoic acid) imidazolines wherein the alkyl group is capryl, undecyl or a mixture of C -C 11 chains, and the disodium salt of lauroyl-cycloimidinium-l-ethoxyethanoic acid-2-ethanoic acid. Moreover, it is sometimes desirable to use combinations of the imidazoline derivatives.

The imidazoline derivatives are normally added in the range of about 0.1-5.0 grams per liter and most desirably about 0.3-1.0 gram per liter. For some of the compositions, the preferred range will fall within the range of about 0.3-3.0 grams per liter. It has been found that the imidazoline concentration is relatively independent of zinc and ammonium concentration, and the derivative appears to improve the quality of the deposit at the higher current density range of above about 50 amperes per square foot.

5. The Brighteners As has previously been indicated, the compositions of the present invention desirably include organic brighteners to impart optimum leveling action of specular brightness over a wide plating range. The brighteners which have been found to provide beneficial effects are selected from the group consisting of aryl ketones, aryl aldehydes, tetrahydroand ring halogenated aryl ketones and aldehydes, heterocyclic aldehydes and ketones, carbocyclic aldehydes and ketones, and aliphatic aldehydes having four to seven carbon atoms.

As specific examples of useful brighteners, the following compounds have demonstrated beneficial results of varying degrees in varying concentrations: ortho-chlorobenzaldehyde, para-chlorobenzaldehyde, benzylidene acetone, coumarin, thiophene aldehyde, cinnamic aldehyde, glutaraldehyde,beta-ionone, l ,2,3 ,6-tetrahydrobenzaldehyde. The preferred brighteners are orthchlorobenzaldehyde, coumarin, thiophene aldehyde and benzylidene acetone. The brighteners may be employed within the range of 002- and are preferably employed in the range of 0.05-0.5 grams per liter.

CONDITIONS OF OPERATION The baths of the present invention may be operated at ambient temperatures of at least about 65 Fahrenheit and up to about 135 Fahrenheit. As the temperature is increased, there is a tendency for the minimum current density for satisfactory plating to increase, and a simultaneous increase in the maximum current density at which satisfactory plating can be obtained. The baths are preferably operated at a temperature of about 70 to 90 Fahrenheit.

The baths of the present invention are effective in a pH range of about 3.0 to about 6.3 The pH is desirably controlled to be within the range of 4.5 to 6.1 and it has been found that the baths tend to stabilize for extended operation in the range of 5.5 to 5.9. The pH of the baths may be adjusted by use of ammonium hydroxide or hydrochloric acid so as to avoid the introduction of possible interfering ions. There appears to be an advantage to operating the baths of the present invention at a pH of above 5.0 since iron contamination tends to precipitate out and minimize contamination of the bath.

The baths exhibit current efficiencies of 96 to 99+ percent throughout the planting-range. The coverage or covering power is at'least equal to the long used cyanide plating baths.

Corrosion problems at the anode are materially reduced by the baths of the present invention so that pure zinc anodes are employed. Moreover, it has been found that even small amounts of metallic impurities in the anodes such as lead, iron and cadmium can be readily solubilized with resultant interference in the optimum operation of the bath. Accordingly, highly refined anodes of high purity are most desirably utilized. Insoluble anodes are not desirable because of the possibility of generating nitrogen trichloride which is highly explosive.

The baths of the present invention provide extremely high conductivity and are operable at very low voltages with high plating efficiencies; moreover, the current efficiency will not tend to vary with the particular components selected and their ratio. For example, a Hull Cell operated at 3 amperes requires the use of only about 2.5-3.0 volts with the preferred composition. The baths exhibit excellent throwing power and covering power over a wide range of current densities so that efficient plating of castings may be effected.

The current densities at which bright deposits are obtained will vary with the particular composition of the bath. Generally, the optimum formulations will provide bright deposits through a range from less than 1.0 amperes per square foot to greater than 100 amperes per square foot. Even with formulations which do not provide a bright deposit of specular reflectivity, adherent bright to dull matte deposits are obtained over a wide range.

It is generally advantageous to employ continuous filtration of the bath through fabric or diatomaceous earth filters since this will tend to remove impurities which might otherwise affect operation of the bath. In order to avoid introduction of impurities, the elements of the filter apparatus should not be metallic.

Agitation by mechanical means tends to improve operation of the bath. The tanks utilized to contain the bath should be non-conductive and non-corrosive; materials such as polyvinyl chloride, polyethylene and polypropylene provide desirable liners for metal tank bodies.

It will be appreciated that the composition of the bath may be monitored readily by titration with ethylene diamine tetraacetic acid in the instance of zinc and silver nitrate in the instance of chloride ion. Makeup of the bath to the desired concentrations and to the adjusted pH is conveniently effected by addition of zinc chloride or oxide, ammonium chloride, ammonium hydroxide or hydrochloric acid, as the case may be.

Exemplary of the efficacy of the present invention are the following specific examples wherein all parts are parts by weight unless otherwise indicated.

EXAMPLE ONE An aqueous bath was prepared containing 68 grams per liter of zinc chloride, 160 grams per liter of ammonium chloride, 7.5 grams per liter of an ethylene oxide/propylene oxide block copolymer having a total molecular weight of about 3,000, an ethylene oxide content of about 40 percent, and an ethylene oxide molecular weight of about 1,250. In addition, the bath includes other surface active agents, namely 0.75 grams per liter of N (alkyl-sulfonyl) glycinesodium salt wherein the alkyl group has an average chain length of 12 carbon atoms, 15 grams per liter of the ammonium salt condensate of naphthalene and sulfonic acid (having average molecular weight of about 600-800) and 0.75 grams per liter of an imidazoline derivative[2-caprylic-l-(ethyl-betaoxipropanoic acid)- imidazoline]. As a brightener 0.05 grams per liter of ortho-chlorobenzaldehyde is employed. The pH is adjusted to 5.0 by addition of ammonium hydroxide.

A series of Hull cell panels is plated at 3.0 amps. for a period of three minutes without agitation while the bath is maintained at a temperature of about F. The resultant panels are found to be bright through a plating range of l-l00 a.s.f.

The pH of the bath is adjusted to about 5.8 by the addition of ammonium hydroxide and a furtherseries of panels is run at the same conditions. Again, specular brightness over a range of l a.s.f. is observed.

EXAMPLE TWO The bath of Example One is employed in a commercial plating tank for rack plating of steel alloy parts having various dimensions and geometric configurations. The bath is maintained at a temperature of about 75 Fahrenheit and a pH of about 5.8. The plating range varies between 20 and 50 a.s.f. and the parts are plated to a thickness of about 0.00025 inch. Upon removal from the bath and rinsing, the parts are found to exhibit specular brightness over their entire surface. The deposits are found to be ductile and adherent.

EXAMPLE THREE A bath is prepared similar in composition to that of Example One except that only the block copolymer is employed as the surface active component and the brightener concentration is increased to 0.1 gram per liter. The pH of the bath is adjusted to about 5.6 and Hull cell panels are plated therewith. These panels are found to-be bright throughout the range of -100 a.s.f. and to exhibit haziness in the range of 1-5 a.s.f.

EXAMPLE FOUR A bath is prepared similar in composition to that of Example One except that the combination of the block copolymer and the glycine compound is used to provide the surface active component. The pH is adjusted to about 5.4. Hull cell panels are again plated with this composition and the panels are found to exhibit specular brightness throughout the range of 1-100 a.s.f.

EXAMPLE FIVE A series of formulations are prepared similar to Example One but substituting for the ortho-chlorobenzaldehyde the following organic brighteners: benzylidene acetone, coumarin, thiophene aldehyde. These compounds provide comparable brightness with variations in the amount required to achieve the desired level of brightness ranging up'to 0.2 gram per liter.

EXAMPLE SIX Baths were prepared similar to that of Example One but utilizing other ethylene oxide/propylene oxide block copolymers having molecular weights ranging from 1,700 to 11,250 and having ethylene oxide contents ranging from 30 percent to 80 percent, all as defined hereinbefore. In some instances it was necessary to increase the amount of the block copolymer in order to obtain comparable quality deposits, but the compositions were otherwise satisfactory.

Thus, it can be seen from the foregoing detailed specification and examples that the present invention provides a zinc plating bath which produces highly adherent and ductile zinc deposits when operated at slightly acid conditions. The bath is usable over a wide range of current densities at high current efficiency and with relatively low consumption of organic components. By use of brighteners, the deposits exhibit specular brightness over a wide plating range. Moreover, the baths are found to exhibit excellent throwing power even upon cast and malleable iron alloys.

Having thus described the invention, we claim:

I. An aqueous bath for producing a ductile, adherent zinc electroplated depositcomprising, on a per liter basis:

a. a soluble zinc salt providing 4-75 grams of zinc as metal and selected from the group consisting of zinc chloride, zinc sulfate, zinc fluoborate, zinc acetate, and mixtures thereof;

b. as an electrolyte, a soluble ammonium salt of hydrochloric acid, sulfuric acid, fluoboric acid, acetic acid, and mixtures thereof, said ammonium salt providing 4-90 grams of ammonium ion, said zinc and ammonium salts providing the designated acid anions in a molar amount at least equal to the combined molar amount of zinc as metal and ammonium ion and within the range of 15-200 grams, said zinc and ammonium salts providing at least about 15 grams of an anion selected from the group consisting of chloride, fluoborate and mixtures thereof; and

c. 2-45 grams of a surface active agent formulation comprising surface active agents selected from the group consisting of:

i. nonionic block copolymers of ethylene oxide and propylene oxide having a total molecular weight of about 1,500-3,500, and an ethylene oxide content of about 35-45 weight percent thereof;

ii. mixtures of anionic N-(alkyl sulfonyl) glycine compounds with nonionic block copolymers of ethylene oxide and propylene oxide having a total molecular weight of about 1,200-l3,000, an ethylene oxide content of about 30-85 weight percent thereof and an ethylene oxide molecular weight of about 500-10,000, the total molecular weight being less than about 5,500 when the ethylene oxide content is 30-40 percent by weight thereof; and

iii. mixtures of either of surface active agents (i) and (ii) with other surface active agents,

said bath having a pH of 3.0-6.3.

2. The bath of claim 1 wherein said bath includes 0.02-1 .5 grams of a brightener.

3. The bath of claim 2 wherein said brightener is selected from the group consisting of aryl ketones, aryl aldehydes, tetrahydroand ring halogenated aryl ketones and aldehydes, heterocyclic aldehydes and ketones, carbocylic aldehydes and ketones, and aliphatic aldehydes having 4-7 carbon atoms.

4. The bath of claim 2 wherein said brightener is ochlorobenzaldehyde.

5. The bath of claim 2 wherein said brightener is benzylidene acetone.

6. The bath of claim 2 wherein said brightener is thiophene aldehyde.

7. The bath of claim 2 wherein said brightener is 1,2 benzopyrone.

8. The bath of claim 1 wherein said surface active agent formulation is agent (iii) and comprises 2.020.0 grams of said block copolymer, 0.1-10.0 grams of said glycine compound, 0.1-5.0 grams of an amphoteric imidazoline derivative having the formula:

Inc-0H2 crnz NE CHQCHzY N=C \G 2. G is a radical selected from the group consisting of -OH, acid salt radicals, anionic surface active sulfate salt radicals, and anionic surface active sulfonate salt radicals;

3. Z is a radical selected from the group consisting of -COOM, CH COOM, and HOCHCH 80 M;

. M is a substituent selected from the group consisting of hydrogen, alkali metals and organic bases;

5. Y is selected from the group consisting of OR and -N(R) A;

. each R'- substituent is independently selected from the group consisting of hydrogen, alkali metals, and (CH )nCOOM;

. A is an anionic monovalent radical;

. n is an integer from 1 to 4; and

. both the groups G and CH,Z are present or absent, and 0.l-l0.0 grams of an anionic condensate of naphthalene and sulfonic acid as the acidv or its soluble salt.

9. The bath of claim 8 wherein said bath includes 002-1 .5 grams of a brightener.

10. The bath of claim 9 wherein said brightener is selected from the group consisting of aryl ketones, aryl aldehydes, tetradydroan ring halogenated aryl ketones and aldehydes, heterocyclic aldehydes and ketones, carbocyclic aldehydes and ketones, and aliphatic aldehydes having 4-7 carbon atoms.

11. The bath of claim 1 wherein said surface active agent formulation is agent (iii) and includes 0.1-5.0 grams of an amphoteric imidazoline derivative having the formula:

Ng-CHQCHiY N=C o wherein:

l. R is an alkyl radical having five to 24 carbon atoms;

2. G is a radical selected from the group consistingof 9. both the groups G and Cl-LZ are present or absent. 12. The bath of claim 1 1 wherein said imidazoline derivative has the formula:

wherein R is an alkyl group having five to 17 carbon atoms; n is an integer of l to 4; and M is hydrogen, NH,

or alkali metal.

13. The bath of claim 12 wherein said imidazoline derivative is 2-caprylic-l-(ethyl-beta-oxipropanoic acid)-imidazoline.

14. The bath of claim 1 wherein said surface active agent formulation is agent (iii) and includes an anionic condensate of naphthalene and sulfonic acid as the acid or soluble salt and in an amount of about 0.l-l0.0 grams.

15. The bath of claim 14 wherein said naphthalene/sulfonic acid condensate is the ammonium salt of a condensate having an average molecular weight of about 500-1 ,000.

16. The bath of claim 1 wherein said zinc salt is at least predominantly zinc chloride and said ammonium salt is at least predominantly ammonium chloride.

17. The bath of claim 16 wherein said zinc chloride is present in an amount providing 7.5-50.0 grams of zinc as metal and said ammonium chloride is present in an amount providing 7.5-50.0 grams of ammonium ion, the total chloride ion content being about 0.75-l.5 of the combined molar amounts of the zinc and ammonium ions.

18. The bath of claim 1 wherein said bath has a pH of about 5.5-5.9.

19. The bath of claim 1 wherein said surface active agent formulation is agent (i) and is present in an amount of about 2.0-20.0 grams and wherein said bath includes 002-1 .5 grams of a brightener.

20. The bath of claim 1 wherein said surface active agent formulation is agent (ii) and said block copolymer is present in an amount of about 2.0-20.0 grams and said glycine compound is present in an amount of about 0. l-l0.0 grams and wherein said bath includes 0.02-1 .5 grams of brightener.

21. In a method for producing a ductile, adheren zinc electroplated deposit on a metallic workpiece, the steps comprising:

A. preparing an aqueous bath comprising, on a per liter basis:

i. a soluble zinc salt providing 4-75 grams of zinc as metal and selected from the group consisting of zinc chloride, zinc sulfate, zinc fluoborate, zinc acetate, and mixtures thereof;

. as an electrolyte, a soluble ammonium salt of hydrochloric acid, sulfuric acid, fluoboric acid, acetic acid, and mixtures thereof, said ammonium salt providing 4-90 grams of ammonium ion, said zinc and ammonium salts providing the designated acid anions in a molar amount at least equal to the combined molar amount of zinc as metal and ammonium ion and within the range of l5-20O grams, said zinc and ammonium salts providing at least about l5 grams of an anion selected from the group consisting of chloride, fluoborate and mixtures thereof; and

iii. 2-45 grams of a surface active agent formulation comprising surface active agents selected from the group consisting of:

a. nonionic block copolymers of ethylene oxide and propylene oxide having a total molecular weight of about l,500-3,500, and an ethylene oxide content of about 35-45 weight percent thereof;

. mixtures of anionic N-(alkyl sulfonyl) glycine compounds with nonionic block copolymers of ethylene oxide and propylene oxide having a total molecular weight of about l,200-l3,000, an ethylene oxide content of about 30-85 weight percent thereof and an ethylene oxide molecular weight of about 500-l0,000, the total molecular weight being less than about 5,500 when the the lene oxide content is 30-40 percent by weight thereof; and

c. mixtures of either of surface active agents (a) and (b) with other surface active agents, said bath having a pH of 3.0-6.3;

B. maintaining said bath at a temperature of about 60 to 135 Fahrenheit;

C. immersing a workpiece having a metallic surface and a zinc anode in said bath; and

D. applying a potential across the anode and workpiece to deposit zinc on said metallic surface, said potential providing a current density of about 1.0-100 amperes per square foot.

22. The method of claim 21 wherein said surface active agent formulation in said bath is agent (iii) and comprises 2.0-20.0 grams of said block copolymer, 0.l-l0.0 grams of said glycine compound, 0.l-5.0 grams of an amphoteric imidazoline derivative having the formula:

Inc-om 01122 N-CHzCHzY N=C \G wherein:

l. R is an alkyl radical having five to 24 carbon atoms;

2. G is a radical selected from the group consisting of -OH, acid salt radicals, anionic surface active sulfate salt radicals, and anionic surface active sulfonate salt radicals;

3. Z is a radical selected from the group consisting of -COOM, Cl-l,COOM, and HOCH-CH, 80 M;

4. M is a substituent selected from the group consisting of hydrogen, alkali metals and organic bases;

5. Y is selected from the group consisting of -OR' and N(R) A;

6. each R substituent is independently selected from the group consisting of hydrogen, alkali metals, and --(Cl-l,)n--COM;

7. A is an anionic monovalent radical;

8. n is an integer from 1 to 4; and

9. both the groups G and C11 2 are present or absent, and O.l-l0.0 grams of an anionic condensate of naphthalene and sulfonic acid as the acid or its soluble salt.

23. The method of claim 22 wherein there is included in said bath 0.02-l.5 grams of a brightener selected from the group consisting of aryl ketones, aryl aldehydes, tetradydroand ring halogenated aryl ketones and aldehydes, heterocyclic aldehydes and ketones, carbocylic aldehydes and ketones, and aliphatic aldehydes having 4-7 carbon atoms.

24. The method of claim 21 wherein said pH is maintained about 5.5-5.9.

25. The method of claim 21 wherein said temperature is maintained about -90 Fahrenheit.

26. The method of claim 21 wherein said potential provides a cathode current density of about l.0-50.0 amperes per square foot.

27. The method of claim 21 wherein there is included in said bath 0.02-l.5 grams of a brightener selected from the group consisting of aryl ketones, aryl aldehydes, tetrahydro and ring halogenated aryl ketones and aldehydes, heterocyclic aldehydes and ketones, carbocylic aldehydes and ketones, and aliphatic aldehydes having 4-7 carbon atoms.

28. The method of claim 21 wherein said surface active agent formulation in said bath is agent (i) and is present in an amount of about 2.0-20.0 grams and wherein said bath includes 0.02-l.5 grams of a brightener.

29. The method of claim 21 wherein said surface active agent formulation in said bath is agent (ii) and said block copolymer is present in an amount of about 2.0-20.0 grams and said glycine compound is present in an amount of about 0. l10.0 grams and wherein said bath includes 0.02-1 .5 grams of brightener.

30. The method of claim 21 wherein said surface active agent formulation in said bath is agent (iii) and includes 0.1-5.0 grams of an amphoteric imidazoline derivative having the formula:

Hie-om cmz N: CHzCHzY N=C o wherein:

l. R is an alkyl radical having tive to 24 carbon atoms;

2. G is a radical selected from the group consisting of -OH, acid salt radicals, anionic surface active sulfate salt radicals, and anionic surface active sulfonate salt radicals;

3. Z is a radical selected from the group consisting of COOM, CH COOM, and HO-CH-Cl-l, $0 M;

4. M is a substituent selected from the group consisting of hydrogen, alkali metals and organic bases:

5. Y is selected from the group consisting of OR' and -N(R');,A;

6. each R substituent is independently selected from the group consisting of hydrogen, alkali metals, and -(Cl-l )nCOOM;

7. A is an anionic monovalent radical;

8. n is an integer from 1 to 4; and

9. both the groups G and CH Z are present or absent. 31. The method of claim 21 wherein said surface ac- 

2. G is a radical selected from the group consisting of -OH, acid salt radicals, anionic surface active sulfate salt radicals, and anionic surface active sulfonate salt radicals;
 2. G is a radical selected from the group consisting of -OH, acid salt radicals, anionic surface active sulfate salt radicals, and anionic surface active sulfonate salt radicals;
 2. G is a radical selected from the group consisting of -OH, acid salt radicals, anionic surface active sulfate salt radicals, and anionic surface active sulfonate salt radicals;
 2. The bath of claim 1 wherein said bath includes 0.02-1.5 grams of a brightener.
 2. G is a radical selected from the group consisting of -OH, acid salt radicals, anionic surface active sulfate salt radicals, and anionic surface active sulfonate salt radicals;
 3. Z is a radical selected from the group consisting of -COOM, -CH2COOM, and HO-CH-CH2SO3M;
 3. The bath of claim 2 wherein said brightener is selected from the group consisting of aryl ketones, aryl aldehydes, tetrahydro-and ring halogenated aryl ketones and aldehydes, heterocyclic aldehydes and ketones, carbocylic aldehydes and ketones, and aliphatic aldehydes having 4-7 carbon atoms.
 3. Z is a radical selected from the group consisting of -COOM, -CH2COOM, and HO-CH-CH2SO3M;
 3. Z is a radical selected from the group consisting of -COOM, -CH2COOM, and HO-CH-CH2SO3M;
 3. Z is a radical selected from the group consisting of -COOM, -CH2COOM, and HO-CH-CH2SO3M;
 4. M is a substitueNt selected from the group consisting of hydrogen, alkali metals and organic bases:
 4. M is a substituent selected from the group consisting of hydrogen, alkali metals and organic bases;
 4. The bath of claim 2 wherein said brightener is o-chlorobenzaldehyde.
 4. M is a substituent selected from the group consisting of hydrogen, alkali metals and organic bases;
 4. M is a substituent selected from the group consisting of hydrogen, alkali metals and organic bases;
 5. Y is selected from the group consisting of -OR'' and -N(R'')3A;
 5. Y is selected from the group consisting of -OR'' and -N(R'')3A;
 5. The bath of claim 2 wherein said brightener is benzylidene acetone.
 5. Y is selected from the group consisting of -OR'' and -N(R'')3A;
 5. Y is selected from the group consisting of -OR'' and -N(R'')3A;
 6. each R'' substituent is independently selected from the group consisting of hydrogen, alkali metals, and -(CH2)n-COOM;
 6. each R'' substituent is independently selected from the group consisting of hydrogen, alkali metals, and -(CH2)n-COOM;
 6. The bath of claim 2 wherein said brightener is thiophene aldehyde.
 6. each R'' substituent is independently selected from the group consisting of hydrogen, alkali metals, and -(CH2)n-COOM;
 6. each R'' substituent is independently selected from the group consisting of hydrogen, alkali metals, and -(CH2)n-COOM;
 7. A is an anionic monovalent radical;
 7. The bath of claim 2 wherein said brightener is 1,2 benzopyrone.
 7. A is an anionic monovalent radical;
 7. A is an anionic monovalent radical;
 7. A is an anionic monovalent radical;
 8. n is an integer from 1 to 4; and
 8. n is an integer from 1 to 4; and
 8. n is an integer from 1 to 4; and
 8. n is an integer from 1 to 4; and
 8. The bath of claim 1 wherein said surface active agent formulation is agent (iii) and comprises 2.0-20.0 grams of said block copolymer, 0.1-10.0 grams of said glycine compound, 0.1-5.0 grams of an amphoteric imidazoline derivative having the formula: wherein:
 9. both the groups G and CH2Z are present or absent.
 9. The bath of claim 8 wherein said bath includes 0.02-1.5 grams of a brightener.
 9. both the groups G and CH2Z are present or absent, and 0.1-10.0 grams of an anionic condensate of naphthalene and sulfonic acid as the acid or its soluble salt.
 9. both the groups G and CH2Z are present or absent.
 9. both the groups G and CH2Z are present or absent, and 0.1-10.0 grams of an anionic condensate of naphthalene and sulfonic acid as the acid or its soluble salt.
 10. The bath of claim 9 wherein said brightener is selected from the group consisting of aryl ketones, aryl aldehydes, tetradydroan ring halogenated aryl ketones and aldehydes, heterocyclic aldehydes and ketones, carbocyclic aldehydes and ketones, and aliphatic aldehydes having 4-7 carbon atoms.
 11. The bath of claim 1 wherein said surface active agent formulation is agent (iii) and includes 0.1-5.0 grams of an amphoteric imidazoline derivative having the formula: wherein:
 12. The bath of claim 11 wherein said imidazOline derivative has the formula: wherein R is an alkyl group having five to 17 carbon atoms; n is an integer of 1 to 4; and M is hydrogen, NH4 or alkali metal.
 13. The bath of claim 12 wherein said imidazoline derivative is 2-caprylic-1-(ethyl-beta-oxipropanoic acid)-imidazoline.
 14. The bath of claim 1 wherein said surface active agent formulation is agent (iii) and includes an anionic condensate of naphthalene and sulfonic acid as the acid or soluble salt and in an amount of about 0.1-10.0 grams.
 15. The bath of claim 14 wherein said naphthalene/sulfonic acid condensate is the ammonium salt of a condensate having an average molecular weight of about 500-1,000.
 16. The bath of claim 1 wherein said zinc salt is at least predominantly zinc chloride and said ammonium salt is at least predominantly ammonium chloride.
 17. The bath of claim 16 wherein said zinc chloride is present in an amount providing 7.5-50.0 grams of zinc as metal and said ammonium chloride is present in an amount providing 7.5-50.0 grams of ammonium ion, the total chloride ion content being about 0.75-1.5 of the combined molar amounts of the zinc and ammonium ions.
 18. The bath of claim 1 wherein said bath has a pH of about 5.5-5.9.
 19. The bath of claim 1 wherein said surface active agent formulation is agent (i) and is present in an amount of about 2.0-20.0 grams and wherein said bath includes 0.02-1.5 grams of a brightener.
 20. The bath of claim 1 wherein said surface active agent formulation is agent (ii) and said block copolymer is present in an amount of about 2.0-20.0 grams and said glycine compound is present in an amount of about 0.1-10.0 grams and wherein said bath includes 0.02-1.5 grams of brightener.
 21. In a method for producing a ductile, adherent zinc electroplated deposit on a metallic workpiece, the steps comprising: A. preparing an aqueous bath comprising, on a per liter basis: i. a soluble zinc salt providing 4-75 grams of zinc as metal and selected from the group consisting of zinc chloride, zinc sulfate, zinc fluoborate, zinc acetate, and mixtures thereof; ii. as an electrolyte, a soluble ammonium salt of hydrochloric acid, sulfuric acid, fluoboric acid, acetic acid, and mixtures thereof, said ammonium salt providing 4-90 grams of ammonium ion, said zinc and ammonium salts providing the designated acid anions in a molar amount at least equal to the combined molar amount of zinc as metal and ammonium ion and within the range of 15-200 grams, said zinc and ammonium salts providing at least about 15 grams of an anion selected from the group consisting of chloride, fluoborate and mixtures thereof; and iii. 2-45 grams of a surface active agent formulation comprising surface active agents selected from the group consisting of: a. nonionic block copolymers of ethylene oxide and propylene oxide having a total molecular weight of about 1,500-3,500, and an ethylene oxide content of about 35-45 weight percent thereof; b. mixtures of anionic N-(alkyl sulfonyl) glycine compounds with nonionic block copolymers of ethylene oxide and propylene oxide having a total molecular weight of about 1, 200-13,000, an ethylene oxide content of about 30-85 weight percent thereof and an ethylene oxide molecular weight of about 500-10,000, the total molecular weight being less than about 5,500 when the the lene oxide content is 30-40 percent by weight thereof; and c. mixtures of either of surface active agents (a) and (b) with other surface active agents, said bath having a pH of 3.0-6.3; B. maintaining said bath at a temperature of about 60* to 135* Fahrenheit; C. immersing a workpiece having a metallic surfAce and a zinc anode in said bath; and D. applying a potential across the anode and workpiece to deposit zinc on said metallic surface, said potential providing a current density of about 1.0-100 amperes per square foot.
 22. The method of claim 21 wherein said surface active agent formulation in said bath is agent (iii) and comprises 2.0-20.0 grams of said block copolymer, 0.1-10.0 grams of said glycine compound, 0.1-5.0 grams of an amphoteric imidazoline derivative having the formula: wherein:
 23. The method of claim 22 wherein there is included in said bath 0.02-1.5 grams of a brightener selected from the group consisting of aryl ketones, aryl aldehydes, tetradydro- and ring halogenated aryl ketones and aldehydes, heterocyclic aldehydes and ketones, carbocylic aldehydes and ketones, and aliphatic aldehydes having 4-7 carbon atoms.
 24. The method of claim 21 wherein said pH is maintained about 5.5-5.9.
 25. The method of claim 21 wherein said temperature is maintained about 70*-90* Fahrenheit.
 26. The method of claim 21 wherein said potential provides a cathode current density of about 1.0-50.0 amperes per square foot.
 27. The method of claim 21 wherein there is included in said bath 0.02-1.5 grams of a brightener selected from the group consisting of aryl ketones, aryl aldehydes, tetrahydro and ring halogenated aryl ketones and aldehydes, heterocyclic aldehydes and ketones, carbocylic aldehydes and ketones, and aliphatic aldehydes having 4-7 carbon atoms.
 28. The method of claim 21 wherein said surface active agent formulation in said bath is agent (i) and is present in an amount of about 2.0-20.0 grams and wherein said bath includes 0.02-1.5 grams of a brightener.
 29. The method of claim 21 wherein said surface active agent formulation in said bath is agent (ii) and said block copolymer is present in an amount of about 2.0-20.0 grams and said glycine compound is present in an amount of about 0.1-10.0 grams and wherein said bath includes 0.02-1.5 grams of brightener.
 30. The method of claim 21 wherein said surface active agent formulation in said bath is agent (iii) and includes 0.1-5.0 grams of an amphoteric imidazoline derivative having the formula: wherein:
 31. The method of claim 21 wherein said surface active agent formulation in said bath is agent (iii) and includes an anionic condensate of naphthalene and sulfonic acid as the acid or soluble salt and in an amount of about 1-10.0 grams. 